The invention relates to an extracorporeal blood circuit, in particular an extracorporeal blood circuit provided with an expansion chamber with a blood filter designed for retaining small bodies (for example blood clots) contained in the blood flow.
Specifically, though not exclusively, the invention can be usefully applied in a blood return line (venous line) of the extracorporeal blood circuit used in a dialysis or hemo(dia)filtration treatment, or another extracorporeal blood treatment which might require the use of an extracorporeal blood circuit.
JP 7299136 describes an expansion chamber for a blood circuit having on a bottom thereof a truncoconical filter having a lower opening which communicates with a blood outlet port. The chamber is superiorly closed by a cover which also exhibits a hole for enabling passage of a tube for inlet of the blood into the chamber.
JP 9140788 describes a blood chamber in which a filter has a tubular filter wall, superiorly closed by a head exhibiting holes, which holes are arranged symmetrically with respect to the axis of the tubular wall and are orientated with the external openings facing upwards.
U.S. Pat. No. 4,676,771 describes an arterial blood filter comprising an expansion chamber having a first port for blood inlet, a second port for blood outlet, a tubular body predisposed in the chamber for preventing passage of non-dissolved gases towards the outlet, and a top head having a fluid-impermeable wall which superiorly closes the tubular body.
DE 3143456 discloses an infusion device provided with a drip chamber internally bearing a holed tubular filtering wall having a top end which is obliquely cut and closed by a cover connected to an upwardly-projecting breather tube. The breather tube prevents the air from moving towards the patient, passing through the lower outlet of the drip chamber.
One of the drawbacks of the expansion chambers used in the extracorporeal blood circuits of known type is connected with the prevention of air bubbles and/or solid particles present in the blood flow passing through the chamber from being transported towards the patient's vascular circuit.
As mentioned above, the prior art includes use of a filter in the venous expansion chambers in order to retain solid particles. These venous filters, however, can retain and facilitate the collecting of air bubbles, especially (but not only) during the stage of priming the extracorporeal blood circuit, i.e. the stage which precedes the actual treatment, in which the extracorporeal blood circuit is emptied of air and filled with a priming fluid. If during this stage the venous filter retains an air bubble, there is the risk that during treatment, with the patient connected up to the extracorporeal circuit, the air bubble might detach from the venous filter and shift towards the patient.